[IPSEC]: Revert ip{,6}_append_data() dst_mtu() conversion.

This patch is wrong.  This is the *one* place where we do need to
use the path MTU.  The reason is that when the packet is fragmented
we only pay for the IPsec overhead once over all and not once for
each fragment.

Please revert it for now.

The trailer_len in ip_append_data is not quite right as the trailer's
length depends on the length of the entire packet.  However, it should
be harmless since ESP knows how to extend the packet when necessary.

Cset exclude: herbert@gondor.apana.org.au|ChangeSet|20050315181807|13007

net/ipv4/ip_output.c

@@ -719,6 +719,7 @@ int ip_append_data(struct sock *sk,
 
 	struct ip_options *opt = NULL;
 	int hh_len;
+	int exthdrlen;
 	int mtu;
 	int copy;
 	int err;
@@ -745,17 +746,22 @@ int ip_append_data(struct sock *sk,
 			inet->cork.addr = ipc->addr;
 		}
 		dst_hold(&rt->u.dst);
-		inet->cork.fragsize = mtu = dst_mtu(&rt->u.dst);
+		inet->cork.fragsize = mtu = dst_pmtu(&rt->u.dst);
 		inet->cork.rt = rt;
 		inet->cork.length = 0;
 		sk->sk_sndmsg_page = NULL;
 		sk->sk_sndmsg_off = 0;
+		if ((exthdrlen = rt->u.dst.header_len) != 0) {
+			length += exthdrlen;
+			transhdrlen += exthdrlen;
+		}
 	} else {
 		rt = inet->cork.rt;
 		if (inet->cork.flags & IPCORK_OPT)
 			opt = inet->cork.opt;
 
 		transhdrlen = 0;
+		exthdrlen = 0;
 		mtu = inet->cork.fragsize;
 	}
 	hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
@@ -764,7 +770,7 @@ int ip_append_data(struct sock *sk,
 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 
 	if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
-		ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
+		ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 		return -EMSGSIZE;
 	}
 
@@ -775,7 +781,7 @@ int ip_append_data(struct sock *sk,
 	if (transhdrlen &&
 	    length + fragheaderlen <= mtu &&
 	    rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
-	    !rt->u.dst.header_len)
+	    !exthdrlen)
 		csummode = CHECKSUM_HW;
 
 	inet->cork.length += length;
@@ -860,9 +866,9 @@ int ip_append_data(struct sock *sk,
 			 *	Find where to start putting bytes.
 			 */
 			data = skb_put(skb, fraglen);
-			skb->nh.raw = data;
+			skb->nh.raw = data + exthdrlen;
 			data += fragheaderlen;
-			skb->h.raw = data;
+			skb->h.raw = data + exthdrlen;
 
 			if (fraggap) {
 				skb->csum = skb_copy_and_csum_bits(
@@ -884,6 +890,7 @@ int ip_append_data(struct sock *sk,
 			offset += copy;
 			length -= datalen - fraggap;
 			transhdrlen = 0;
+			exthdrlen = 0;
 			csummode = CHECKSUM_NONE;
 
 			/*

net/ipv6/ip6_output.c

@@ -850,13 +850,13 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to, int offse
 		np->cork.rt = rt;
 		inet->cork.fl = *fl;
 		np->cork.hop_limit = hlimit;
-		inet->cork.fragsize = mtu = dst_mtu(&rt->u.dst);
+		inet->cork.fragsize = mtu = dst_pmtu(&rt->u.dst);
 		if (dst_allfrag(&rt->u.dst))
 			inet->cork.flags |= IPCORK_ALLFRAG;
 		inet->cork.length = 0;
 		sk->sk_sndmsg_page = NULL;
 		sk->sk_sndmsg_off = 0;
-		exthdrlen = opt ? opt->opt_flen : 0;
+		exthdrlen = rt->u.dst.header_len + (opt ? opt->opt_flen : 0);
 		length += exthdrlen;
 		transhdrlen += exthdrlen;
 	} else {